<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        html, body {
            height: 100%;
            margin: 0;
        }

        .wrapper {
            min-height: 100%;

            /* Equal to height of footer */
            /* But also accounting for potential margin-bottom of last child */
            margin-bottom: -50px;
        }

        .footer,
        .push {
            height: 50px;
        }
    </style>
</head>
<body>
<div class="wrapper">

    content

    <div class="push" style="background-color: #6c757d"></div>
</div>
<footer class="footer" style="background-color: #005cbf"></footer>
</body>
</html>